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From: David Kastrup <dak@gnu.org>
To: 17485@debbugs.gnu.org
Cc: David Kastrup <dak@gnu.org>
Subject: bug#17485: [PATCH 3/3] Reimplement reduce-right in srfi-1
Date: Tue,  3 Jun 2014 20:56:18 +0200	[thread overview]
Message-ID: <1401821778-19972-3-git-send-email-dak@gnu.org> (raw)
In-Reply-To: <1401821778-19972-1-git-send-email-dak@gnu.org>

* module/srfi/srfi-1.scm (reduce-right): Avoid use of drop-right in
  connection with last as a single upfront reverse is more efficient and
  simpler to understand.

Signed-off-by: David Kastrup <dak@gnu.org>
---
 module/srfi/srfi-1.scm | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/module/srfi/srfi-1.scm b/module/srfi/srfi-1.scm
index 73d164a..6aa249a 100644
--- a/module/srfi/srfi-1.scm
+++ b/module/srfi/srfi-1.scm
@@ -573,10 +573,7 @@ then that's the return value."
 F is on two elements from LST, rather than one element and a given
 initial value.  If LST is empty, RIDENTITY is returned.  If LST
 has just one element then that's the return value."
-  (check-arg procedure? f reduce)
-  (if (null? lst)
-      ridentity
-      (fold-right f (last lst) (drop-right lst 1))))
+  (reduce f ridentity (reverse lst)))
 
 (define map
   (case-lambda
-- 
1.9.1






  parent reply	other threads:[~2014-06-03 18:56 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-05-13 10:47 bug#17485: (srfi srfi-1) reduce-right does not scale, version 2.0.9 David Kastrup
2014-06-01 23:41 ` Mark H Weaver
2014-06-02  7:59   ` David Kastrup
2014-06-03 18:56 ` bug#17485: [PATCH 1/3] Let length+ return the length of dotted lists rather than #f David Kastrup
2014-06-03 18:56   ` bug#17485: [PATCH 2/3] Rewrite take-right, drop-right, drop-right! David Kastrup
2014-06-04  3:29     ` Mark H Weaver
2014-06-04  3:45     ` Mark H Weaver
2014-09-20 14:56     ` Mark H Weaver
2014-09-20 15:15       ` David Kastrup
2014-09-22 17:15         ` Mark H Weaver
2014-09-22 18:40           ` David Kastrup
2014-06-03 18:56   ` David Kastrup [this message]
2014-06-04  3:30     ` bug#17485: [PATCH 3/3] Reimplement reduce-right in srfi-1 Mark H Weaver
2014-06-04  3:42   ` bug#17485: [PATCH 1/3] Let length+ return the length of dotted lists rather than #f Mark H Weaver
2014-06-04  4:57     ` David Kastrup
2014-06-04 10:09       ` David Kastrup
2014-06-05 13:57         ` David Kastrup
2016-06-21 14:42 ` bug#17485: (srfi srfi-1) reduce-right does not scale, version 2.0.9 Andy Wingo
2016-06-21 15:31   ` David Kastrup
2016-07-12  7:07     ` Andy Wingo
2016-07-12  7:43 ` bug#17485: Ugh, well David Kastrup
2016-07-12 13:54   ` Andy Wingo

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